Sewer Main Condition Assessment in the Last Frontier

The Anchorage Water and Wastewater Utility (AWWU) owns, operates, and maintains a sewer pipe network with over 750 miles of pipe ranging from 2 inch lateral pipe to 96 inch interceptors consisting of 15 different pipe materials. AWWU currently has over 26 miles of sewer interceptors, as classified with the Strahler Stream Order analysis that have been installed periodically since 1917. The average age of the interceptors is 33 years. Like many utilities across the country and around the world, AWWU is trying to become more proactive and less reactive in its maintenance of its critical assets. To be in a position to plan ahead, AWWU realized that they needed first hand additional data on the condition of its sewer conveyance system. Through its asset management program, AWWU used the limited data available on the existing interceptors to organize them into risk categories based upon the probability and consequence of their failure. AWWU then retained a team lead by CH2M HILL's Condition Assessment and Rehabilitation Service group (CARS) with subconsultant services provided by Red Zone Technologies to perform a condition assessment of all major risk interceptors and as much of the major and moderate risk trunks and lateral pipe that could be obtained given the limited project budget. The work includes approximately 111,000 LF of large diameter, high risk sewer interceptors, 10,000 LF of high risk force main interceptors, and 75,000 LF of high and moderate risk sewer laterals. The project was approached using a streamlined tiered and adaptive plan (TAP) that focuses data collection while still making sure that all of the assets are included in the work. The result is the collection of the data required to complete detailed condition assessments of the existing AWWU assets, predict future (remaining) life of the assets and accurately schedule future repair/rehabilitation/replacement efforts. The key to the applied system is: 1. identifying and managing project issues early; 2. executing a tiered approach to data collection and analysis and, 3. applying the right data to rehabilitation recommendations This was a huge undertaking and everything is susceptible to the weather conditions prevalent to Anchorage. While work started in August of 2011, it ended in December. The completion of this undertaking relied on close coordination between the AWWU O&M staff and Administration and CH2M HILL. Work included confined space entries, significant traffic control to inspect MH's and run CCTV/Sonar/Laser equipment, snow removal, agency access permits, operations running 24 hours per day (two shifts of 12 hours each) and a significant public relations effort. The main focus of this paper and presentation will be the logistical and coordination efforts required to perform the condition assessments. This presentation will also cover:AWWU Asset Management Planning;Background of Project;Selection of Condition Assessment Technologies for this project; Presentation of findings from the work; and Knowledge Gained.